1. Field of the Invention
This invention relates to a control apparatus, and more particularly to a power transmission control apparatus for use with a vehicle having a power generator.
2. Description of the Related Art
Typically, a vehicle capable of supplying electricity to external electric appliances includes an engine having a crankshaft, a power generator spaced apart from the engine, and a power transmitting device. The power transmitting device includes a power transmitting unit for transmitting controllably a power from the crankshaft, and a switching unit for driving the power transmitting unit. The switching unit is operable to switch the power transmitting unit between a supplying state and a non-supplying state. In the non-supplying state, the crankshaft cannot drive the power transmitting unit. In the supplying state, the crankshaft can drive the power transmitting unit to enable the power generator to generate electricity.
Referring to FIG. 1, the switching unit 11 of the power transmitting device includes a switching rod 12 for driving the power transmitting unit, a stepper motor 13 spaced apart from the switching rod 12, and a gear assembly 14 driven by the stepper motor 13. The stepper motor 13 drives the gear assembly 14 to rotate the switching rod 12 to thereby change the power transmitting unit between the supplying state and the non-supplying state.
The stepper motor 13 is disposed for controlling accurately the rotational angle and position of one of gears of the gear assembly 14 by poise signals to drive rotation of the switching rod 12 between a supplying position and a non-supplying position. In this manner, the switching rod 12 can be positioned accurately. However, the stepper motor 13 is more expensive than a DC motor. Furthermore, if it is desired to adjust the angle and position of the stepper motor 13 or increase the torque and power of the stepper motor 13, the structure of the stepper motor 13 needs to be changed largely, thereby resulting in waste in time and cost.